This application is based on Japanese Patent Application No. 2001-062862 filed on Mar. 7, 2001, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates in general to an electric-component mounting system arranged to mount electric components (typically, electronic components) on a circuit substrate, and more particularly to techniques for improving the efficiency of mounting of the electric components.
2. Discussion of Related Art
JP-A-6-342998 discloses an example of an electric-component mounting system including a plurality of component-holding heads which are arranged around a common axis of turning and turned about this common axis, to mount electric components on a circuit substrate. The component-holding heads are disposed on an indexing body rotatable about a vertical axis, such that the component-holding heads are equiangularly spaced apart from each other along a circle having a center on the vertical axis of rotation of the indexing body. With a rotary intermittent motion of the indexing body, the component-holding heads are turned about the vertical axis of rotation of the indexing body (which is the above-indicated common axis of turning of the heads). The indexing body has a plurality of working positions or stations at which the component-holding heads are temporarily stopped. These working positions includes a component-receiving position and a component-mounting position. At the component-receiving position, the component-holding head receives an electric component from a component supply device. At the component-mounting position, the electric component is transferred from the component-holding head onto the circuit substrate.
Each of the component-holding heads includes a plurality of suction nozzles, and a nozzle holder which holds those suction nozzles and is rotatable about an axis thereof to bring a selected one of the suction nozzles into the operating position. The nozzle holder is rotated by a nozzle-holder rotating device, and has an engaging portion. The nozzle-holder rotating device is disposed at one of the above-indicated plurality of working positions, and includes an engaging member engageable with and disengageable from the engaging portion of the nozzle holder, for rotating the nozzle holder so as to select one of the suction nozzles held by the nozzle holder. Conventionally, a head turning device including the indexing body for turning the component-holding heads about the above-indicated common axis of turning is held off until the desired suction nozzle has been brought into the operating position by the nozzle-holder rotating device. Where a nozzle-selecting time required for bringing the desired suction nozzle into the operating position is longer than the times required for completing the other working operations such as the time required for the component-holding heads to receive and hold the electric components and the time required for the heads to mount the electric components on the circuit substrate, the time during which the head turning device must be held off is determined by the nozzle-selecting time, which is the longest required working time. Thus, the nozzle-selecting time may be one of factors that lower the efficiency of component-mounting operations of the electric-component mounting system.
It is therefore an object of the present invention to provide an electric-component mounting system which assures an improvement in the efficiency of mounting of electric components. This object may be achieved according to any one of the following modes of the present invention in the form of an electric-component mounting system, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) An electric-component mounting system comprising:
a plurality of nozzle holders each of which carries a plurality of suction nozzles and is rotatable to bring a selected one of the suction nozzles into an operating position thereof, the each nozzle holder having an engaging portion:
a turning device operable to turn the plurality of nozzle holders about a common axis of turning, for sequentially stopping each of the nozzle holders at a plurality of predetermined working positions including a nozzle-selecting position, a component-receiving position and a component-mounting position, so that the each nozzle holder receives an electric component at the selected one suction nozzle placed in the operating position, when the each nozzle holder is located at the component-receiving position, and mounts the electric component onto a circuit substrate when the each nozzle holder is located at the component-mounting position;
a holder rotating device including an engaging member engageable with and disengageable from the engaging portion of the each nozzle holder, the holder rotating device being disposed at the nozzle-selecting position and operable to rotate the nozzle holder located at the nozzle selecting position, while the engaging member is in engagement with the engaging portion; and
an engaging-and-disengaging device operable to move the engaging member for engagement and disengagement with and from the engaging portion,
wherein the holder rotating device is arranged to rotate the engaging member, while permitting a movement of the engaging member in at least a direction of turning of each nozzle holder by turning device.
In the electric-component mounting system according to the above mode (1) of this invention, the holder rotating device is arranged to rotate the engaging member, while permitting a movement of the engaging member in the direction of turning of the nozzle holders by the turning device. This arrangement permits a rotary motion of the engaging member to be transmitted to the engaging portion of each nozzle holder, while the engaging member is moved in the direction of turning of the nozzle holder. Accordingly, at least a portion of the rotary motion of the nozzle holder to bring a selected one of the suction nozzles into the operating position can be effected while the nozzle holder is turned by the turning device. Conventionally, the rotation of the nozzle holder to select the desired suction nozzle is effected only while the nozzle holder is stopped at the nozzle-selecting position, that is, only while the turning of the nozzle holder is suspended. In this conventional arrangement, the nozzle holder is required to be stopped at the nozzle-selecting position for a comparatively long time, and this long stop time of the nozzle holder may be a factor that lowers the efficiency of mounting of the electric components. The holder rotating device arranged according to the present invention makes it possible to effectively avoid such a drawback. The holder rotating device may have a specific arrangement as described below with respect to the following mode (2), for rotating the engaging member while permitting the engaging member to be moved in at least the direction of turning of the nozzle holder by the turning device. However, the arrangement of the holder rotating device according to the following mode (2) is not essential. For instance, the holder rotating device may be arranged to rotate the engaging member while the holder rotating device as a whole is permitted to be moved in the direction of turning of the nozzle holder.
(2) An electric-component mounting system according to the above mode (1), wherein the holder rotating device further includes (i) a rotary member holding the engaging member and rotatable with the engaging member, (ii) a rotary drive device operable to rotate the rotary member and the engaging member, and (iii) a rotation transmitting device interposed between the engaging member and the rotary member and operable to transmit a rotary motion of the rotary member to the engaging member, while permitting the engaging member to be moved in at least the direction of turning of each nozzle holder by the turning device,
and wherein the engaging-and-disengaging device moves the engaging member in an axial direction of the rotary member, for effecting engagement and disengagement of the engaging member with and from the engaging portion of each nozzle holder.
The holder rotating device provided according to the above mode (2) uses a relatively simple arrangement, namely, the rotation transmitting device interposed between the engaging member and the rotary member, for rotating the engaging member to rotate the nozzle holder while permitting the movement of the engaging member in the direction of turning of the nozzle holder by the turning device.
(3) An electric-component mounting system according to the above mode (1) or (2), wherein the engaging-and-disengaging device is operable to hold the engaging member in engagement with the engaging portion of each nozzle holder, for at least a predetermined period of time after initiation of a turning movement of each nozzle holder by the turning device from the nozzle-selecting position toward the component-receiving position.
In the electric-component system according to the above mode (3) wherein the engaging member is held in engagement with the engaging portion of the nozzle holder even after the turning movement of the nozzle holder from the nozzle-selecting position toward the component-receiving position, the engaging member is rotated to rotate the nozzle holder for bringing the selected suction nozzle into the operating position, while the engaging member is moved in the direction of turning of the nozzle holder as the nozzle holder is turned. Accordingly, the nozzle holder is not required to be held stopped at the nozzle-selecting position until the selected suction nozzle has been brought into the operating position. Thus, a sufficient time can be obtained for engagement of the engaging member with the engaging portion of the nozzle holder to rotate the nozzle holder for bringing the desired suction nozzle into the operating position, while reducing the required time of stopping of the nozzle holder at the nozzle-selecting position. The reduction of the stopping time of the nozzle holder makes it possible to reduce the required time of mounting of the electric components on the circuit substrate, leading to improved efficiency of operation of the system. Further, the engagement of the engaging member with the engaging portion of the nozzle holder may be initiated at a given point of time before the nozzle holder reaches the nozzle-selecting position. This arrangement also results in reducing the required time of stopping of the nozzle holder at the nozzle-selecting position. Usually, however, it is easier to hold the engaging member in engagement with the engaging portion even after the initiation of the turning movement of the nozzle holder from the nozzle-selecting position, than to initiate the engagement of the engaging member with the engaging portion during the turning movement of the nozzle holder to the nozzle-selecting position.
(4) An electric-component mounting system according to the above mode (2) or (3), wherein the rotation transmitting device permits the engaging member to be moved relative to the rotary member in all radial directions of the rotary member.
In the above mode (4), the engaging member can be smoothly moved in the direction of turning of the nozzle holder, following the turning movement of the nozzle holder by the turning device.
(5) An electric-component mounting system according to the above mode (4), wherein the rotation transmitting device includes an Oldham""s coupling.
The rotation transmitting device may include a connecting shaft, and two universal joints, for instance. However, the rotation transmitting device preferably includes an Oldham""s coupling or sliding coupling, which is comparatively simple and compact in construction.
(6) An electric-component mounting system according to any one of the above modes (2)-(5), wherein the holder rotating device includes a positioning device which normally holds a predetermined relative position of the engaging member and the rotary member, and which permits a movement of the engaging member from the predetermined relative position when a force acts on the engaging member in the direction of turning of each nozzle holder.
In the electric-component mounting system according to the above mode (6) wherein the predetermined relative position of the engaging member and the rotary member is maintained by the positioning device, the engaging member can be precisely brought into engagement with the engaging portion of the nozzle holder. When a force is applied to the engaging member in the direction of turning of the nozzle holder, the positioning device permits a movement of the engaging member from the predetermined position relative to the rotary member, so that the engaging member can be held in engagement with the engaging portion during at least a portion of the turning movement of the nozzle holder.
(7) An electric-component mounting system according to the above mode (6), wherein the positioning device includes at least one spring which is held in engagement with the engaging member and the rotary member, at respective opposite ends thereof.
The above-indicated at least one spring may be at least one spring in the form of a rod or wire. In this case, each rod or wire spring is fixed at its fixed end to one of the engaging member and the rotary member, such that the rod or wire spring extends in the axial direction of the rotary member, while the free end is fitted in a hole formed in the other of the engaging member and the rotary member.
(8) An electric-component mounting system according to the above mode (7), wherein the at least one spring consists of at least three plate springs which are arranged in a circumferential direction of the rotary member, each of the at least three plate springs being fixed at a fixed end thereof to one of the engaging member and the rotary member, and extending toward the other of the engaging member and the rotary member, each plate spring being held in contact with the above-indicated other of the engaging member and the rotary member such that each plate spring is slidable on the above-indicated other of the engaging member and the rotary member.
The plate springs are preferably disposed such that biasing forces of these plate springs act on the engaging member and the rotary member, in radial directions of the rotary member, so as to hold the engaging member and the rotary member in a coaxial relationship with each other. For instance, the plate springs are disposed symmetrically with each other with respect to the axis of the rotary member. This arrangement is effective to hold the engaging member and the rotary member in the coaxial relationship with each other. However, the symmetrical arrangement is not essential. While the plate springs may take the form of straight strips or sheets, the plate springs may take any other forms. For instance, each plate spring may have a curved intermediate portion which is curved in the radially outward direction of the rotary member, and two straight end portions which extend in the axial direction of the rotary member.
(9) An electric-component mounting system according to any one of the above modes (2)-(8), wherein the holder rotating device includes:
a stationary rotary drive source; and
an axial-movement permitting device interposed between the stationary rotary drive source and the rotary member and operable to transmit a rotary motion of the rotary drive source to the rotary member while permitting a movement of the rotary member in an axial direction thereof.
(10) An electric-component mounting system according to any one of the above modes (2)-(8), wherein the holder rotating device includes:
a first rotary shaft disposed such that the first rotary shaft is rotatable and axially immovable;
a second rotary shaft disposed such that the second rotary shaft is rotatable and axially movable;
a connecting device which connects the first and second rotary shafts to each other, so as to permit an axial movement of the second rotary shaft relative to the first rotary shaft;
an axially moving device operable to move the second rotary shaft in the axial direction; and
a stationary rotary drive source operable to rotate the first rotary shaft,
and wherein the second rotary shaft functions as the rotary member, while the axially moving device functions as the engaging-and-disengaging device.
(11) An electric-component mounting system according to any one of the above modes (1)-(10), wherein each nozzle holder is rotatable about an axis which is perpendicular to the common axis of turning of the plurality of nozzle holders.
(12) An electric-component mounting system according to any one of the above modes (1)-(11), wherein the engaging portion of each nozzle holder has a plurality of straight engaging grooves formed in an end face of each nozzle holder which is perpendicular to an axis of rotation of each nozzle holder, the straight engaging grooves intersecting each other on the axis of rotation of each nozzle holder, the engaging member including a straight engaging tooth which is engageable with a selected one of the plurality of straight engaging grooves, and wherein the nozzle rotating device is operable to rotate the engaging member to an angular position in which the straight engaging tooth extends in a direction substantially parallel to a line of tangency to a circle along which each nozzle holder is turned, the straight engaging tooth extending in the direction substantially parallel to the above-indicated line of tangency when the straight engaging tooth is engaged with or disengaged from the selected one straight engaging groove.
In the electric-component mounting system according to the above mode (12), the engaging tooth is engaged with or disengaged from the engaging portion of each nozzle holder, with the engaging tooth extending in a direction parallel to or substantially parallel to the line of tangency to the circle along which the nozzle holders are turned. While the engaging tooth extends in the above-indicated direction, the engagement of the engaging tooth with the engaging portion can be initiated even where the engaging tooth and the engaging portion are misaligned with each other by a relatively large amount in the radial direction. In other words, the engaging member and the engaging portion may be relatively easily misaligned while the engaging member and the engaging portion are held in engagement with each other. The arrangement according to the above mode (12) is effectively combined with the feature according to the above mode (1) or (2) that the engaging member is movable in the direction of turning of the nozzle holder. Namely, a portion of the rotary motion of the nozzle holder required to bring the selected suction nozzle into the operating position can be effected with increased stability during a turning movement of the nozzle holder by the turning device.
(13) An electric-component mounting system according to any one of the above modes (1)-(12), wherein the turning device includes:
an indexing body rotatable about the common axis of turning of the nozzle holders;
an intermittently rotating device operable to rotate the indexing body at a predetermined angular pitch; and
a plurality of nozzle-holder holding members disposed on the indexing body such that the nozzle-holder holding members are spaced apart from each other in a circumferential direction of the indexing body, the nozzle-holder holding members holding the plurality of nozzle holders, respectively, such that each nozzle holder is rotatable.
(14) An electric-component mounting system according to the above mode (13), wherein each of the nozzle-holder holding members comprises a holder shaft disposed on the indexing body such that the holder shaft is rotatable, the electric-component mounting system further including a nozzle rotating device operable to rotate the holder shaft for rotating the corresponding nozzle holder about a centerline of the selected suction nozzle placed in the operating position.
(15) An electric-component mounting system according to the above mode (13) or (14), wherein each of the nozzle-holder holding members comprises a holder shaft disposed on the indexing body such that the holder shaft is axially movable, the electric-component mounting system further including a nozzle moving device operable to move the holder shaft in an axial direction for moving the corresponding nozzle holder in a direction parallel to a centerline of the selected suction nozzle placed in the operating position.